Continuous production of aldol



May 15, l945- F. J. METZGER 4 2,376,070

CCNTINUOUS PRODUCTION OF ALDOL Y Filed Feb. 12, 1943 ATTORNEYS Patented May l5, 1945 coNTmUoUsraonoqrroN or 3 ,Q

imminence.

Herrmann-ignorano Reduction (.ltlnpanyyA N.Y..aoporatlonoi'NewYork vNew York,

application February 12, 1943, ser-mno. '415,622

rcmm. (claws-soz) This invention relates to the manufacture of aldol and particularly tev a continuous cyclic method of condensing aeetaldehyde to produce aldol in a commercially practicable and economical manner.

Aldol is formed by the condensation of two molecules of acetaldehvde ZCHJCHO-*CHJCHOHCHaCHO The condensation iseflted in the presenceof an Yalkaline agent such as an alkalimetal hydroxide or a carbonate or an alkaline earth metal oxide.

The condensation or aldolization reaction is exothermic and liberates considerable quantities of heat, i. e.` 235 B. t. u. per pound of acetaldehyde condensed. Furthermore the liberation oi' the heat and the resulting rise in temperature if the heat is not promptly removed, are irregular and diilicult to control. If the temperature is not controlled eectively, the increase in temperature will accelerate the reaction with the result that additional heat is released. There is a marked tendency for the reaction to proceed to the point where all ot theacetaldehyde is converted to a useless water insoluble resin.

If, during the reaction, the temperature is allowed to rise excessively or the time of reaction' is unduly prolonged, the product is contaminated with substances of higher molecular weight than aldol, such as higher polymers of aldol and aldehyde resins. These products decrease the yield of aldol and resultin a product of poor quality. Since the distillation of aldol may be can'ied out only with considerable dimculty and loss, the

separation of higher boiling products from aldol is not economically feasible.

Because o! thevdiillculty of controlling the reaction1 aldol has been prepared by a batch procedure. It has been suggested that control may be more readily effected by diluting the acetaldehyde with water. This procedure introduces the further dimculty :that the aldol contains a large quantity of water which must be removed subsequently at considerable cost.

It is the object of the. present invention to provide `an eilective and economical method of producing aldol by. condensation which avoids the difficulties mentioned and permits continuous production of a satisfactory higher boilingimpurities.y

Other objects and advantages ot the invention will be apparent ,aait is better understood by reference tothe following `speciiication and the vproduct tree vfrom mmmaticallyan apparatus suitable for the practice of the invention.

I have discovered that the condensation of acetaldehyde to aldol can be controlled satisfactorily and that aldol can be produced in a continuous mannerby cycling a. solution of acetaldehyde in aldol through a temperature-controlled reaction chamber and adding acetaldehyde and an alkaline catalyst to the cycled solution. The dilution of Vthe acetaldehyde with aldol restrains the visor ot the condensation reaction and Darticularly the irregular liberation-ot heat therefrom. It is possible, therefore. to remove the heat eiecvely and to maintain the desired temperature of the reaction withinpractical limits.

An amount of the solution equivalent to the additions is withdrawn continuously from the cycle and neutralized with an acid to prevent further reaction. This solution, principally aldol, will contain some unreacted acetaldehyde, a small amount of water, and the-neutralized cats.`

lyst, but it is free from undesirable higher polymerization products of aldol.

A higher yield of aldol may be obtained if the u portion of the solution withdrawn from the cycle accomvnyinsrdrawing, which ilhistrates dia-"55 is permitted to react furtherunder controlled temperature conditions for a brief Periodbeiore the catalyst is neutralized. This. additional reaction is preferred, but it is not essential to the invention as described, since-the initial reaction can be conducted and controlled to afford a satisfactory product. :v f

The temperature of the reaction must be controlled within relatively narrow limits and preferably within the range of 20?t0 40 C. It may be somewhat lower or higher. At a, temperature `of 15 C., the reaction is ordinarilytoo slow, and

at a temperature of 50 C. it tends to be too rapid. Normally. as hereinbefore indicated, it is extremely difllcult to` control the temperature of the reaction,-but by conducting it in the manner indicated no diiilculty is experienced' in holding the temperature within the ldesired range by means ot ordinary cooling devices such as a jacketed vessel, a. coil within a cooling bat-h, or multi- -ple tubes surrounded by a.` cooling medium.

Water or any: other suitable liquid `may be used asthecoolingagent. f :i

The catalyst employed may be any of the usual alkaline agents such las thel hydroxides or carbonates of the alkali metals or-the oxides of the alkaline earth metals or similar agents. Sodium hydroxide is the preferredicatalyst. The amount of catalyst employed will depend to some extent upon the amoimt of free acid'contained in the ably inthe form .sired, it may .alyst acetaldehyde. Freshly distilled acctaldehyde containslittleornofreeamhutmstnnding aidoimproaweamsuomisaeuvered pipeandisdeliveredtothereceptaclellfor neutralization.

Asanexampieofthehxventimassumingan apparatusasdescribedwithareaction chamber, returnpipecirculatlngpmnpandotherneceasaryfeedandexitlineshavhigavolumeofapproximatelylcuhicfootandacoolhigsurtace ofapproximatelymareeetmledwitha 60% aldol, 40% acetaldehyde solution containa ingsuilidentcatalystmtheformoi'awatersolutionofsodiumhydroxidetogiveaplofapproximately10tothereactionmixture,thepump maybeopentedtocyolethesolutionthrough thereaconchamhercttherate oi approximatelyiwgallonsperhourwhilethetemperatureof thereactionchamherheld atapproximately 30 C. To thissystem ls fed continuously acetaldehydeotacommercialgradeattlierateof approximately 6.0 pounds per hour and 4.5%

.aqueoussodiumhydroxideattherateotabout Reierringlaotliedrawing,iindicatestliexeal=-` tionchambcrhavingajackctwlchmaybe water or other cooling agentv Thecoolhlgaswteslle .'amountofasomuonofthewystwgiveapn of ll-lltothecyclingmixtureisinixodwcdfrna tinuouslyfedinthemanneraboveeitcdtomaintainapHotQ-llwithinthecycledsohdion. In thcreactionchamberlthcacctalddlyeiscondensed at a. temperaturecmtroiled within the desiredranzehw the circulationofthe cooling agentthroughthejackett. v

'Iheaolutionescapesthroughapipe liandis returned through a pipe It surrounded hy a jacket-llthroughwhichwaterorothercooling throughthepump lltothereachonchamber 5, Therateofcirculamismaintainedto ensuretliemosteectlvereaction. w

Aportionottliesolutioniswithdrawncontinumxslythroushapipellwhichisconnectedwith tretment. Intheevcntthatadditionalrwctionisiiesired,aya.ive2linthcpipe22hcledanda valve Slinahranch pipe Ilisopencdtodcliver reacliitll` thesohttiontoanauxiliary chamber asintheresetlonvchamber tionssuhstantiall! mision withtheresultthatahighu' 0.55 pound per hour. From the cycle approximatelyspolmdspcrhourofthereactionmixture are withdrawn, having a specific gravity at 15 C. o! about 1.065. This solution is neutralized with the catalyst. The product consists of approximately 52% aldol, 36% aoetaldchyde, 12% waterandsomesodimnacetate,butisfreefrom high boiling impurities.

By utilizing the auxiliary reaction chamber l2. thus allor-ding a longer time for the reaction, the aldol contentofthennishedproductmaybe increased to Gil-70% with corresponding reductionintheproportionofacetaldehyde. By varyingotherconditions,theyleldoaldolcanbe The foregoing example is merely illustrative of the preferred conditions o! operation Acetic acidisindicatedastheneutralizingasent, but any acid auch as hydrochloric or sulphuric, etc., maybeemployed. Insomecasesthestepot neutralizhig may he omitted. for example, when theproductistobesubiectedimmedlatelyto somefurthertreaunent, or where the catalyst used is substantially neutral or slightly acid. Theinventiondoesnotdependupontheuseoi can be varied over wide ranges without materiallyalteringtheresuitsattained.

Theinvention affords procedure permittlng continuous production ot aldol free fromhigher boiling impurities. It avoidsthehighcostdbatchoperationsandthe diiiicultiesinhermtintheadditiondlargequantitieaotwntertothesolution.

variouschangesmaybcmadeintheprocedure and the swarm: without departing from the inventionorsacrlilcingthcadvantagesthereof.

Iclaim:

'fmsaidbomsauingmsddwspmoiths wlthdrswnsoluon to neutralile the alkaline talyltthermaddingacsaldehydcandaikaiino ca of 1l catalysttoanotherpartoithewithdnwnportion a. simple and .effective` 2. The method of producing aldol by condensa;-v

tion of acetaldehyde which comprises maintaining a body of a solution of acetaldehyde'and an a1- kaline catalyst in aldol; controlling fthetemperature of saidbody of Solution. substantially continuously withdrawing a portion of thesolution from said body adjacent one'en'd thereof, adding an acid to a part of the withdrawn solution to neutralize the alkaline catalyst therein, adding acetaldehyde and alkaline catalyst to another part of the withdrawn portion of the solution, and returning the part of the solution to which the acetaldehyde and alkaline catalyst were added to said body of solution adjacent the other end thereof.

3. The method of producing aldol by'condensation of acetaldehyde which comprises maintaining a, body of a solution of acetaldehyde and an alkaline catalyst in aldol, maintaining Vthe temperature of said body between 20 C. and 40 C., adding an acid to a part of the withdrawn solution to neutralize the alkaline catalyst therein,

adding acetaldehyde and alkaline catalyst to another prt of the withdrawn portion of the solution, and returning the part of the solution to which the acetaldehyde and alkaline catalyst were added to said body of solution. A

4. The method of producing aldol by condensation of acetaldehyde which comprises maintaining a body of a solution of acetaldehyde and an alkaline catalyst in aldol, controlling the temperature of said body of solution, substantially continuously withdrawing a portion of the solution from said body,.adding an acid to a part of the withdrawn solution to neutralize -the alkaline catalyst therein, cooling another part of the withdrawn portion of the solution, adding acetaldehyde and alkaline catalyst to the cooled part of the withdrawn portion of the solution, and returning the part of the solution which was cooled and to which the acetaldehyde and alkaline catalyst were added to said body of solution.

5. The method of producing aldol by condensation of acetaldehyde which comprises maintaining a. body of a solution of acetaldehyde and an alkaline catalyst in aldol, controlling the temperature of said body of solution, substantially f continuously withdrawing a DOrtion of the solution from said body, maintaining a part of the CERTIFICATE Patent no. 2,576,070.

withdrawn solution under conditions such that condensation of the acetaldehyde therein continues for a further period of time, thereafter adding an acid to said part of the withdrawn portion of the solution to neutralizethe alkaline `catalyst therein, adding acetaldehyde and alkaline catalyst to another part of the withdrawn portion of the l solution, andreturningthepartof the solution to which the acetaldehyde alkaline catalyst were added to said body of solution.4

6,'The method of producing aldol by condensation of acetaldehyde which comprises maintaining a body of a solution of acetaldehyde and an alkaline catalyst in aldol, controlling the temperature of said body of solution, substantially continuously withdrawing a portion of the solution from said body, adding an acid t0 a part of the withdrawn solution to neutralize the alkaline catalyst therein, adding acetaldehyde and alkaline catalyst to another part of the withdrawn portion of the solution, and returning the part of the solution to which the acetaldehyde and alkaline catalyst were added to said body of solution, the amount of alkaline catalyst added to the returned part of the Withdrawn solution being sufficient to maintain a pH o f from about 9 to l1 in said body of solution.

'7. The method of producing aldol by condensation of acetaldehyde which comprises maintaining a body of a solution of acetaldehyde and an alkaline catalyst in aldol, maintaining the temperature of said body between 20 C. and 40 C., substantially continuously withdrawing a portion of the solution from said body, maintaining a part of the withdrawn solution under conditions such that condensation of the acetaldehyde therein continues for a. further period of time, thereafter adding an -acid to said part of the withdrawn portion of the solution to neutralize the alkaline catalyst therein, cooling another part of the withdrawn portion of the solution, adding acetalde- FLOYD J' HETZG-ER.

hyde and alkaline catalyst to said cooled part of the withdrawn portion of the solution, and returning the part of the solution which was cooled and to which the acetaldehyde and alkaline catalyst were added to said body ofsolution, the alkaline catalyst being added to the cooled part of the solution in an amount suiiicient to maintain a pH of from about 9 to 11 in said body of solution.

FLOYD J. METZGER..

coRRscTIoN. i

May l5 It ls hereby certified that error appears in the printed specification of the above numbered patent -requiring correction ss follows Page 5 first column, une 25,'c1a1m5. after "llo c.,

"' insert substantially continuously withdrawing a'portion of the solution from said body,; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the oase in the Patent Office.

signed and sealed this Jimi day of August, A. D. 19ll5.

( Seal) Leslie Frazer First Assistant Commissioner of Patents.

2. The method of producing aldol by condensa;-v

tion of acetaldehyde which comprises maintaining a body of a solution of acetaldehyde'and an a1- kaline catalyst in aldol; controlling fthetemperature of saidbody of Solution. substantially continuously withdrawing a portion of thesolution from said body adjacent one'en'd thereof, adding an acid to a part of the withdrawn solution to neutralize the alkaline catalyst therein, adding acetaldehyde and alkaline catalyst to another part of the withdrawn portion of the solution, and returning the part of the solution to which the acetaldehyde and alkaline catalyst were added to said body of solution adjacent the other end thereof.

3. The method of producing aldol by'condensation of acetaldehyde which comprises maintaining a, body of a solution of acetaldehyde and an alkaline catalyst in aldol, maintaining Vthe temperature of said body between 20 C. and 40 C., adding an acid to a part of the withdrawn solution to neutralize the alkaline catalyst therein,

adding acetaldehyde and alkaline catalyst to another prt of the withdrawn portion of the solution, and returning the part of the solution to which the acetaldehyde and alkaline catalyst were added to said body of solution. A

4. The method of producing aldol by condensation of acetaldehyde which comprises maintaining a body of a solution of acetaldehyde and an alkaline catalyst in aldol, controlling the temperature of said body of solution, substantially continuously withdrawing a portion of the solution from said body,.adding an acid to a part of the withdrawn solution to neutralize -the alkaline catalyst therein, cooling another part of the withdrawn portion of the solution, adding acetaldehyde and alkaline catalyst to the cooled part of the withdrawn portion of the solution, and returning the part of the solution which was cooled and to which the acetaldehyde and alkaline catalyst were added to said body of solution.

5. The method of producing aldol by condensation of acetaldehyde which comprises maintaining a. body of a solution of acetaldehyde and an alkaline catalyst in aldol, controlling the temperature of said body of solution, substantially f continuously withdrawing a DOrtion of the solution from said body, maintaining a part of the CERTIFICATE Patent no. 2,576,070.

withdrawn solution under conditions such that condensation of the acetaldehyde therein continues for a further period of time, thereafter adding an acid to said part of the withdrawn portion of the solution to neutralizethe alkaline `catalyst therein, adding acetaldehyde and alkaline catalyst to another part of the withdrawn portion of the l solution, andreturningthepartof the solution to which the acetaldehyde alkaline catalyst were added to said body of solution.4

6,'The method of producing aldol by condensation of acetaldehyde which comprises maintaining a body of a solution of acetaldehyde and an alkaline catalyst in aldol, controlling the temperature of said body of solution, substantially continuously withdrawing a portion of the solution from said body, adding an acid t0 a part of the withdrawn solution to neutralize the alkaline catalyst therein, adding acetaldehyde and alkaline catalyst to another part of the withdrawn portion of the solution, and returning the part of the solution to which the acetaldehyde and alkaline catalyst were added to said body of solution, the amount of alkaline catalyst added to the returned part of the Withdrawn solution being sufficient to maintain a pH o f from about 9 to l1 in said body of solution.

'7. The method of producing aldol by condensation of acetaldehyde which comprises maintaining a body of a solution of acetaldehyde and an alkaline catalyst in aldol, maintaining the temperature of said body between 20 C. and 40 C., substantially continuously withdrawing a portion of the solution from said body, maintaining a part of the withdrawn solution under conditions such that condensation of the acetaldehyde therein continues for a. further period of time, thereafter adding an -acid to said part of the withdrawn portion of the solution to neutralize the alkaline catalyst therein, cooling another part of the withdrawn portion of the solution, adding acetalde- FLOYD J' HETZG-ER.

hyde and alkaline catalyst to said cooled part of the withdrawn portion of the solution, and returning the part of the solution which was cooled and to which the acetaldehyde and alkaline catalyst were added to said body ofsolution, the alkaline catalyst being added to the cooled part of the solution in an amount suiiicient to maintain a pH of from about 9 to 11 in said body of solution.

FLOYD J. METZGER..

coRRscTIoN. i

May l5 It ls hereby certified that error appears in the printed specification of the above numbered patent -requiring correction ss follows Page 5 first column, une 25,'c1a1m5. after "llo c.,

"' insert substantially continuously withdrawing a'portion of the solution from said body,; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the oase in the Patent Office.

signed and sealed this Jimi day of August, A. D. 19ll5.

( Seal) Leslie Frazer First Assistant Commissioner of Patents.

vDi'selaimel' y 2,376,070.-Floyd J. Metzger, New York, N. Y. Commons Pnonnre'rrouV or ALnoL. Patent dated May 15, 1945. Disclaimer filed Nov. 4, 1947, by the inventor;

the assignee, A'ir Reduction Company, Incorporated, assenting. Hereby enters this disclaimer'to claims 1 to 7 inclusive of said Letters Patent.

l [0 0cial-l0azelfe December 9, 1.947.] 

